[Paper Review] Accurate single- and double-differential resummation of colour-singlet processes with MATRIX+RadISH: $W^+W^-$ production at the LHC

Stefan Kallweit, Emanuele Ré+2 more|arXiv (Cornell University)|Apr 16, 2020

Particle physics theoretical and experimental studies175 references53 citations

TL;DR

The paper develops a Matrix+RadISH interface to perform high-accuracy resummation (N3LL) matched to NNLO for colour-singlet production, and applies it to full leptonic WW production with fiducial cuts, obtaining NNLO+N3LL and NNLO+NNLL predictions for multiple observables.

ABSTRACT

We present the combination of fully differential cross sections for colour-singlet production processes at next-to-next-to-leading order (NNLO) QCD obtained with MATRIX and all-order resummation through RadISH. This interface allows us to achieve unprecedented accuracy for various transverse observables in $2 \ ightarrow 2$ production processes. As an important application we consider $W^+ W^-$ production at the LHC, more precisely the full leptonic process $pp\ o \\ell^+\\ell^{\\prime\\, -}\ u_{\\ell}{\\bar\ u}_{\\ell^\\prime}+X$ with $\\ell'\ eq\\ell$, and we present resummed predictions for differential distributions in presence of fiducial selection cuts. In particular, we resum the transverse-momentum spectrum of the $W^+ W^-$ pair at next-to-next-to-next-to-leading logarithmic (N$^3$LL) accuracy and match it to the integrated NNLO cross section. The transverse-momentum spectrum of the leading jet in $W^+ W^-$ production is calculated at NNLO+NNLL accuracy. Finally, the joint resummation for the transverse-momentum spectrum of the $W^+ W^-$ pair in the presence of a jet veto is performed at NNLO+NNLL. Our phenomenological study highlights the importance of higher-order perturbative and logarithmic corrections for precision phenomenology at the LHC.

Motivation & Objective

• Provide fully differential NNLO QCD predictions for colour-singlet processes using an NNLO+resummation framework.
• Achieve N3LL resummation for transverse observables and match to NNLO cross sections.
• Apply the framework to WW production with full leptonic final state and fiducial cuts.
• Offer multi- and double-differential resummation (pT, pT^J) including jet veto scenarios.

Proposed method

• Interface Matrix with RadISH to perform all-order resummation of transverse observables in colour-singlet production.
• Use qT-subtraction in Matrix to assemble NNLO cross sections with a controlled r_cut extrapolation.
• Employ RadISH in momentum space to resum logarithms to N3LL accuracy for pT and related observables.
• Perform NNLO+N3LL (and NNLO+NNLL) matching of resummed results to fixed-order cross sections.
• Utilize the RadISH double-differential formalism to obtain pT and pT^J spectra with vetoes, fully differential in Born kinematics.

Experimental results

Research questions

• RQ1 How can one achieve high-precision, multi-differential resummation for colour-singlet processes at NNLO accuracy?
• RQ2 What is the impact of N3LL resummation on the transverse momentum spectra of the colour-singlet system and associated jets?
• RQ3 How does the Matrix+RadISH interface perform for WW production with full leptonic final states and fiducial cuts?
• RQ4 What are the improvements in jet-vetoed cross sections and jet-associated observables when combining NNLO with NNLL/N3LL resummation?
• RQ5 Can double-differential resummation in pT and pT^J with jet-veto conditions be reliably achieved and matched to NNLO?

Key findings

• Resummed predictions for WW production at NNLO+N3LL accuracy for the W+W− pair pT spectrum in the presence of fiducial cuts.
• NNLO+NNLL predictions computed for the transverse momentum of the leading jet (pT^J) in WW production.
• Joint NNLO+NNLL resummation for the WW pair pT with a jet-veto constraint.
• The interface enables resummation for essentially any colour-singlet process with two-loop amplitudes available.
• Demonstrated phenomenological significance of higher-order perturbative and logarithmic corrections for precision LHC phenomenology.
• Comparison with ATLAS data for fiducial WW cross sections under jet-veto conditions is highlighted.